The present invention relates to systems and methods for broadband communication between a network and a customer premise along a line of sight path.
Local Multipoint Distribution System (LMDS) in an existing architecture involves broadcasting microwave signals at frequencies at or above 28 gigahertz to small receiver dishes, typically installed on the top of apartment buildings. At that high frequency, line of sight is required for maximum signal performance. The received LMDS signal may then be distributed through the building. In general, existing LMDS systems use the LMDS receiver to serve one customer or subscriber, with each different customer or subscriber having a single dedicated LMDS receiver.
Current microwave links, including LMDS links, are designed to compensate for a number of fades. One type of fade is known as a fast fade. A fast fade occurs when a signal reaches a receiver by taking two paths of different lengths. Different path lengths may cause partially destructive or totally destructive interference, resulting in a noisy or faded signal. Because of the highly directional and the fixed nature of LMDS links (and other line of sight links), these links do not exhibit significant fast fades. The fast fades that are experienced cause limited bit and cell errors, which may be readily cleaned up by forward error correction.
Another type of fade is the long term fade. That is, weather may cause a long term fade. For example, rain causes long term fade of high frequency signals. Long term fades are generally addressed through power control and link budget design.
And lastly, another type of fade that is particularly cumbersome in LMDS and other line of sight applications such as microwave links (above about 12 Gigahertz) and infrared links, is the long term obstruction. A long term obstruction is an obstruction that may last as much as a few minutes or longer. In particular, a long term obstruction is something that interrupts the line of sight which is required for LMDS links and other links sufficiently high in frequency to require line of sight.
Although existing deployment of LMDS (and other line of sight technology including microwave links above about 12 Gigahertz and infrared links) has been quite limited, the higher frequencies and additional bandwidth associated therewith is not yet being utilized to its full potential. For the foregoing reasons, there is a need for line of sight communication systems and methods that are capable of compensating for long term obstructions that interfere with the required line of sight during communication.
It is, therefore, an object of the present invention to provide a system and method for broadband communication between a network and a customer premise along a line of sight path that utilizes a redundant or secondary link to overcome the problems associated with long term obstructions.
In carrying out the above object, a system for broadband communication between a network and a customer premise along a line of sight path is provided. The system comprises a customer premise equipment and at least one transmitter in communication with the network and configured to transmit at a sufficiently high frequency to require line of sight. The customer premise equipment has a first directional antenna operative to communicate in a first line of sight. The customer premise equipment also has a second directional antenna operative to communicate in a second line of sight that is different than the first line of sight. The at least one transmitter, the first antenna, and the second antenna are located so as to form a primary communication path along the first line of sight and to form a redundant communication path along the second line of sight.
In one embodiment, the at least one transmitter further comprises a first transmitter and a second transmitter. The first transmitter is located within the first line of sight and selectively operative to communicate with the first antenna along the primary communication path. The second transmitter is located within the second line of sight and selectively operative to communicate with the second antenna along the redundant communication path. Preferably, the system further comprises network control logic configured to select one of the primary and redundant communication paths based on a status of the first and second lines of sight. That is, the network control logic permits transmission by the first transmitter when the primary path is selected and permits transmission by the second transmitter when the redundant path is selected. Utilizing network control logic to only transmit from the transmitter having a clear line of sight is particularly useful when the first and second antenna are in close proximity to each other to reduce potential for interference in the system.
In another embodiment, the at least one transmitter is a single transmitter within the first line of sight and within the second line of sight. The first and second antennas are sufficiently spaced apart to separate the primary and redundant communication paths. In such an implementation, because the first and second antennas are sufficiently spaced apart to separate the primary and redundant communication paths, it may be preferable to omit the network control logic and allow each transmitter to transmit simultaneously. Accordingly, this embodiment preferably further comprises customer premise control logic configured to select one of the primary and redundant communication paths based on signal quality at the first and second antennas due to a status of the first and second lines of sight. That is, all of the transmitters may transmit and the selection of the appropriate communication path is made at the customer premise.
It is to be appreciated that in embodiments of the present invention, the at least one transmitter may include any number of hubs connected to the network, in addition to including any number of repeaters operative to communicate through a hub to the network. That is, based on local geography, the final connection to the customer premise to establish a communication path may be from the customer premise antenna to a hub or to a repeater (or from a plurality of antennas to a plurality of hubs and/or repeaters).
Preferably, in embodiments of the present invention, the customer premise equipment further includes a decoder configured to decode communications received at the first and second antennas. It is to be appreciated that an antenna may be connect to the customer premise local equipment in a variety of ways. For example, the antenna may be connected to the local equipment by a fiber, a coaxial cable, or a twisted pair. In a suitable implementation utilizing coaxial cable to connect an antenna to the customer premise, the decoder is located at the customer premise and the antenna connects to the coaxial cables through a converter to down convert communications to an intermediate frequency.
In a suitable fiber implementation, the decoder is located at the customer premise local equipment and the converter may be omitted as appropriate. Further, when a twisted pair is used to connect the antenna to the customer premise local equipment, it is preferred that the decoder be located at the antenna to decode the signal prior to transmission along the twisted pair. Of course, it is to be appreciated that an appropriate connector such as twisted pair, fiber, or coaxial cable, may be selected based upon the distance between the antenna and the customer premise local equipment.
Further, embodiments of the invention may be implemented with the sufficiently high frequency in the Local Multipoint Distribution System (LMDS) frequencies. Further, embodiments of the present invention may utilize sufficiently high frequencies with an infrared frequency. Or, other appropriate sufficiently high frequencies may be found at frequencies greater than about 12 Gigahertz.
Further, in carrying out the present invention, a system for broadband communication between a network and a customer premise along a line of sight path is provided. The system comprises a customer premise equipment and at least one transmitter in communication with the network and configured to transmit at a sufficiently high frequency to require line of sight. The customer premise equipment has a plurality of directional antennas operative to communicate in a corresponding plurality of lines of sight. The at least one transmitter and the plurality of antennas are located so as to form a corresponding plurality of redundant communication paths along the plurality of lines of sight.
Still further, in carrying out the present invention, a system for broadband communication between the network and the customer premise along a line of sight path is provided. The system comprises a customer premise equipment, a primary transmitter in communication with the network, a secondary transmitter in communication with the network, and network control logic. The customer premise equipment has a directional antenna operative to communicate in a line of sight. The primary transmitter is configured to selectively transmit at a sufficiently high frequency to require line of sight. The primary transmitter and the antenna are located so as to form a primary communication path along the line of sight. The secondary transmitter is configured to selectively transmit at a frequency sufficient to communicate absent line of sight. The secondary transmitter and the antenna are located so as to form a secondary communication path. The network control logic is configured to select the primary communication path when the line of sight is clear, and to select the secondary communication path when the line of sight is blocked by, for example, a long term obstruction.
It is to be appreciated that this embodiment of the present invention, utilizing a primary and a secondary transmitter, allows a lower frequency non-line of sight link to be used as a backup for a primary communication path that does require line of sight. Further, it is to be appreciated that the customer premise equipment may, if desired, include two antennas, one for communication with the primary transmitter and another for communication with the secondary transmitter, instead of including only a single antenna.
Yet further, in carrying out the present invention, a method for broadband communication between a network and a customer premise along a line of sight path is provided. The method comprises establishing a primary communication path, establishing a redundant communication path, and selecting one of the primary and redundant communication paths.
The primary communication path extends between a first directional antenna and a first transmitter along a first line of sight. The first transmitter is configured to transmit at a sufficiently high frequency to require line of sight. The redundant communication path extends between a second directional antenna and a second transmitter along a second line of sight. The second transmitter is configured to transmit at a sufficiently high frequency to require line of sight. One of the primary and redundant communication paths is selected based on a status of the first and second lines of sight. That is, if one of the lines of sight is interrupted by a large obstruction, the other line of sight is selected for the communication path.
In one suitable implementation, the first and second transmitters are different transmitters. In another suitable implementation, the first and second transmitters are the same transmitter, and the first and second antennas are sufficiently spaced apart to separate the primary and redundant communication paths.
Even further, in carrying out the present invention, a method for broadband communication between a network and a customer premise along a line of sight is provided. The method comprises establishing a primary communication path configured for a sufficiently high frequency to require line of sight, and establishing a secondary communication path for a frequency sufficient to communicate absent line of sight. The method further comprises selecting the primary communication path when the line of sight is clear, and selecting the secondary communication path when the line of sight is blocked by a large obstruction.
The advantages associated with embodiments of the present invention are numerous. For example, systems and methods of the present invention provide architectures for LMDS applications and other sufficiently high frequency applications requiring line of sight communications that overcome the problem of large obstructions associated with systems and methods of the prior art. That is, embodiments of the present invention either employ primary and redundant communication paths at line of sight frequencies, or employ a primary communication path at the high frequency and a secondary communication path at a lower frequency sufficient to communicate absent line of sight, allowing appropriate control logic either at the network or at the customer premise to overcome the problems associated with large obstructions by utilizing the appropriate communication path to avoid the obstruction.